It creates a conflict of interest for the attorneys. It sets a precedent that wealthy people can receive faster treatment from the SEC. Of course, the SEC tends to investigate people who have made large amounts of money through potentially illegal means, so this may not be an issue. However, it also provides less incentive for the SEC to move quickly on other cases. If the SEC can accept money in exchange for speeding up the process, they are now one step away from slowing down or drawing out the whole process as a means for extorting money.